The present invention generally relates to an in vivo surgical instrument and, more particularly, to a surgical instrument suited, but not exclusively limited thereto, for use in an ophthalmic surgical operation for the removal of the diseased vitreous.
It is well known that in ophthalmic surgical operations a surgical cutting instrument is utilized to remove the diseased vitreous. According to the state of art, the surgical cutting instrument is available in various types. One surgical cutting instrument comprises an outer tube having a distal end, and an inner tube having a distal end which is axially slidably inserted in the outer tube. The outer tube has a perforation defined therein at a position axially and inwardly of the distal end thereof. The distal end of the inner tube, and a peripheral lip region, defining the aperture in the outer tube, cooperate with each other to provide a scissor action when the inner tube is axially moved relative to the outer tube.
In order to improve cutting performance, the inner tube should be designed so as to move along the curved outer tube so that, during the axial movement of the inner tube relative to the outer tube, an outer peripheral surface of the inner tube and an inner peripheral surface of the outer tube can fit into one another as perfectly as possible.
Another known surgical cutting instrument similarly comprises an outer tube having a distal end and a perforation defined therein adjacent the distal end thereof, and an inner tube having a distal end which is axially slidably inserted in the outer tube. In order to improve cutting performance, the distal end of the inner tube is flared axially outwardly so that the axially outwardly flared distal end of the inner tube and a peripheral lip region defining the aperture in the outer tube cooperate with each other to provide a scissor action when the inner tube is axially moved relative to the outer tube.
It has, however, been found that any one of the above discussed prior art surgical cutting instruments have their own problems. Specifically, in the surgical cutting instrument utilizing the outer tube curved so as to permit the inner tube to slide in tight contact with the inner peripheral surface of the outer tube, a difficulty has often been encountered in making an access to and withdrawal from the site of surgical operation because of the curved feature. Also, the employment of the curved feature in the outer tube obviously results in an enlargement of the aperture defined therein and, therefore, during the access to and the withdrawal from the site of surgical operation, a texture adjacent the site of surgical operation may be inadvertently scratched.
On the other hand, in the prior art surgical cutting instrument wherein the distal end of the inner tube is flared axially outwardly, the axial outwardly flared distal end of the inner tube serves as a movable blade which cooperates with the peripheral lip region of the aperture in the outer tube which serves as a stationary blade. Considering that the axially outwardly flared feature in the distal end of the inner tube has been employed for the purpose of providing a sharp cutting action during the relative movement of the inner tube within the outer tube, the repetition of this relative movement brings about a quick wear of the movable blade resulting not only in a reduction in cutting performance, but also in a reduction in the lifetime of the surgical cutting instrument.
Accordingly, the present invention has been devised to provide an improved surgical cutting instrument capable of exhibiting a sharp cutting performance for a substantially prolonged period of use.
Another important object of the present invention is to provide an improved surgical cutting instrument of the type referred to above, which is readily and easily accessible to a site of surgical operation in order to remove an affected tissue without substantially causing retraumatization of the surgical site.